The desire to simultaneously measure “everything” in any sample has driven the development of artificial “noses” and “tongues”. These devices have been based on a wide variety of sensor array strategies. Examples of sensor arrays include those based on cantilevers, conducting polymers, electrochemistry, photonics, the piezoelectric effect, or surface acoustic waves. In a photon-based sensor, one requires a photon source, appropriate sensing chemistry (i.e., a recognition element), a means to immobilize the desired sensing chemistry so it may be reused, and a photon detector. All reported photon-based sensor arrays depend on at least one photon source (e.g., lamps, lasers, light emitting diodes) and all currently used photon sources in photon-based sensor arrays require electrical power. This need for electrical power limits any photonically-based sensor device.
Although a number of strategies exist for developing photonically-based sensor arrays (vide supra), there is clearly a need for new strategies that use little or no electrical power. Specifically, there is a need for devices wherein the photon/light source operates without any external electrical power. Hieftje and coworkers (Rev. Sci. Instrum. 1999, 70:50-57) introduced the idea of using a beta emitter, 90Sr, and a liquid or plastic scintillator in concert with time-correlated single photon counting as a pulsed photon source for the determination of excited-state fluorescence lifetimes.
A system has been developed to address the limitations of existing sensor array photon sources. Our source system can potentially work with any photonically-based chemical sensor modality. It consists of a sealed 90Sr beta emitter (with or without a scintillator), a chemical responsive sensor array, and an array-based photodetector. It can serve as part of a complete photonically-based sensor array system that has two major features. First, the photon source does not require any electrical power and the source can be operated continuously, in an unattended manner, for several years. Thus, electrical power is only needed to power the photodetector in this system. Second, the so formed photonic sensor array is capable of the detection and/or quantification of more than one analyte in a sample at the same time.